Fluid pressure control mechanism



E. R. FITCH FLUID FRESSURE CONTROL MECHANISM June `29, 1948.

3 Sheets-Sheet 1 Filed 00'0. 5l, 1944 QnNbUdRmL.

WN WN 1 INVENTOR. Ellely R. l'c/L.

A TTR/VEYS June 29, 194s.

Filed oop. 5 1, 1944 E'PAILER E. R. FITCH FLUID PRESSURE CONTROL MECHANISM 5 Sheets-Sheet 2 INVENToR.

Ellel/ R. FL'CL.

` ATTORNEYS June 29, 1948. E. R. FITCH 2,444,190

FLUID PRESSURE CONTROL MECHANISM Filed Oct. 51, 1944 Y 5 Sheets-Sheet 3 v 4&5 MASTER coNTRoLLER 734 33 4] /42 6I I, 'in M474 qe 4 46 l 2O' 2 Wm ft 'uw IN VEN TOR. BYElzefy R. Fife/L.

ATTORNEYS Patented June 29, 1948 2,444,190 FLUID PRESSURE CONTROL MECHANISM Ellery R.

Westinghouse Elyria, Ohio, a corpora Fitch, Elyria, Ohio, assignor to Bendix- Automotive Air Brake Company,

tion of Delaware Application October 31, 1944, Serial No. 561,256

10 Claims.

This invention relates to fluid pressure control mechanism, and more particularly to uid pressure control mechanism of the electropneumatic type for controlling the operation of vehicle brakes.

It has previously been proposed to employ electromagnet valve mechanisms for assisting in the control of the brakes on vehicles in order to obtain a more satisfactory and efficient remote control and a more rapid application and release of the brakes, but many of these systems have had a disadvantage from the standpoint of safety and efficient operation, and it is accordingly an object of the present invention to provide electropneumatic fluid pressure control mechanism of the above type, so constituted as to overcome these difficulties.

Another object of the invention is to provide, in a fluid pressure control mechanism of the above type, means for insuring positive and coordinated control of the energization and deenergization of the electromagnetic control valves under the control of the vehicle operator.

A further object of the invention is to provide, in a system of the above type, means controlled in accordance with the operation of the brake valve for controlling the energization and deenergization of the electromagnet valves, so constituted as to permit a direct control by the operators brake valve of the supply and release of iiuid pressure to and from the brake actuators in the event of failure of the electrical portion of the system.

Still another object of the invention is to provide, in a system of the above type, a controller for controlling the energization and de-energization of the electromagnet application and release valves, so constituted as to be capable of ready attachment to existing fluid pressure control systems of conventional type, without appreciably changing the characteristics of such systems and Without requiring the use -of separate types of fluid pressure control valves in the conventional portion of the system.

Another object of the invention is to provide fluid pressure operated means for positively controlling and actuating the operation of switches of the snap action type in the circuits of the electromagnet valves.

A still further object of the invention is to provide, in a controller for a system of the above type, operating connections between a pressure responsive switch operating member and the switches so constituted as to permit movement of the member after operation of the switches for the purpose of permitting the member to establish direct communication between the operators control valve and the fluid pressure operated device or actuator.

Yet another object of the invention is to provide, in connection with a system of the electropneurnatic type having a iiuid pressure operated valve of the relay emergency type adapted to effect an emergency application of the brakes in response to a drop in pressure at the source, means for supplying fluid pressure from the source to the electrom-agnet valves so constituted as to prevent the operation of the latter valves from interfering with the normal functions of the relay emergency valve.

Other objects and novel features of the invention will appear more fully from the following detailed description when taken in connection with the accompanying drawings, which illustrate one embodiment of the invention. It is to be eX- pressly understood, however, that the drawings are employed for purposes of illustration only, and are not designed as a defini-tion of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings, wherein characters refer to similar parts throughout several views Fig. 1 is a diagrammatic view, partially in section, of an electropneumatic brake system for a tractor constructed in accordance with the principles of .the present invention,

Fig. 1a is a diagrammatic view of the coordinated system for use on a trailer drawn by the tractor;

Fig. 2 is a partial sectional view of a controller mechanism for the system shown in Fig. l, and

Fig. 3 is a fragmentary sectional view of a switch and the .actuating mechanism therefor forming a part of the controller.

Referring more particularly to Fig. l of the drawing, a fluid pressure brake system for a -tractor is illustrated as comprising in general a supply reservoir B supplied with fluid pressure from a compressor, not shown, through a conduit 1, a brake actuator 8 adapted to operate a brake lever 9 as shown, a fluid pressure operated device or relay valve I0 of conventional type having a control line Il, a supply line l2, an outlet line I3 connected to the actuator as shown, and an exhaust port, not shown, for exhausting fluid pressure from the actuator on corresponding action of the relay valve. The supply line i2 is connected with a second reservoir I4 which is supplied with iuid pressure from the main ressimilar reference the ervoir E by means of a conduit I 5. Without showing the construction of the relay valve in detail, it will be understood by those skilled in the art that on application of iiuid pressure to the upper end oi the relay valve through the control conduit il, the conduits I2 and I3 will be connected and fluid pressure will be supplied from the reservoir I4 to the actuator 8 at a pressure substantially the same as that existing in the conduit H, while release of fluid pressure from the conduit II results in a corresponding decrease in the pressure supplied to the actuator by the relay valve Iii. The system also includes a self-lapping operators control valve or r lie valve I6 of conventional type, which may be constructed in accordance with the principles set forth in the patent to William J. Andres and Roy Sanford, No. 2,133,275, dated October i8, i938. The brake valve IS is supplied with fluid pressure from the reservoir 6 by means of a conduit I and is connected with the conduit II by means oi a conduit I il, the brake valve fur-ther being provided with an exhaust conduit I3 as shown. A brake pedal 2li is provided for operating the brake valve, and it will be understood that with the brake pedal in the position shown, the brake valve is effective to establish communication between conduits I 8 and I 9 and to prevent communication between conduits I'I and I8. When the brake pedal is depressed, communication between conduits i3 and It, is interrupted and communication established between conduits Il' and I il, the mechanism of the valve being such that the pressure suppliedr to the conduit I8 is substantially proportional `to the degree of movement of the pedal 20 from the position shown. Since the conduit i8 is connected with the conduit II, it will be understood that on operation of the pedal 25| to eiect an application of the brakes, iluid pressure will, in the ordinary course oi events, be supplied to the conduit II and to .the upper end of .the iiuid pressure operated device or relay valve it, whereupon the latter will be effective to supply fluid pressure from the reservoir I4 to the actuator 8 at a pressure substantially the same as that obtaining in the conduit I I.

The fluid pressure brake system, above described, is of conventional design and is in common use. In View of the fact that in most cases the relay valve In is remotely situated from the brake valve considerable delay is often times experienced in supplying fluid pressure from the brake valve to the upper end or the relay valve, and this delay is reflected as a distinct delay in the application of fluid pressure to the actuator 8. In order to overcome this undesirable condition, various means have been proposed in the past for incorporating electrically operated valves of the magnet type in the system in order to provide` a more instantaneous supply of fluid pressure to the relay valve or other devices being actuated, and in the present instance a magnet valve 2I is provided of the so-called duplex type, and is adapted to supply fluid pressure directly from the.

reservoir I to the conduit I8 which is connected to the control conduit II leading to the upper end of the relay valve I il, this magnet valve being preferably located directly adjacent the relay valve I and the reservoir I4. The magnet valve 2| is preferably of the type illustrated in the patent to Wilfred A. Eaton, No. 2,234,897, dated March 11, 1941, the valve comprising an application portion 22 provided with a normally closed inlet valve, not shown, and a release or exhaust portion 23, provided with a normally closed exhaust valve, likewise not shown. The application portion 22 oi the valve is supplied with iiuid pressure from the reservoir Ill by means of a conduit 21, and is provided with an outlet line 25 conneoted with the conduit It, the outlet line also being connected with the exhaust portion 23 of the valve by means of a conduit Z6. The exhaust portion of the valve is provided with an exhaust conduit and electromagnets, not shown, of the portions Z2 are provided with terminals 2e and il@ and and il respectively. Since, as heretofore stated, both the inlet and exhaust valves are normally in closed position when the magnets are energized, it will be understood that communication is normally prevented 1between conduits l/l and 25 as well as between conduits 2li and When the portion 22 is energized by proper connections to the terminals 28 and 29, conduits and 25 are connected to supply fluid pressure from the reservoir ill to the conduit I3 and thence to the upper end of the relay valve Il) through conduit il. In the event the right portion is energized, a connection is established between conduits 2G and El, and fluid pressure is exhausted from the top of the relay valve through conduit il, conduit I8, conduit 25, conduit 25, the magnet valve portion 23 and exhaust conduit 2l'.

In order that the magnet valve 25 may be properly controlled in accordance with the operation of the brake valve Ill, a controller 32 is provided and interposed in the conduit I8 as will be more fully explained hereinafter. Referring more particularly to Fig. 2 of the drawing, the main portion of this controller includes a casing 33 provided with a cylindrical passage 3d having a port 35 at its right and a port 3S at the leit end, the port i6 being connected to the left hand portion of the conduit it shown in Fig. 1 and the port Sli being connected to right hand portion of the conduit. el rod 3l is slidably mounted in bores 36 and 39 formed in the opposite end of the casing concentric with the passage 34, and a piston 49 is suitably attached to the center of the rod for movement therewith as shown. A preferably V-shaped annular ring 'lI is formed on the inner surface ci the passage and centrally disposed as shown, and is so dimensioned at its center as to be in substantially sliding engagement with the outer .surface of the piston. The piston thus forms, in connection with the passage, a right hand chamber l2 connected with the port 35 and a left hand chamber connected with the port 36, the piston in the position shown serving to prevent communication between the chambers. In order that the piston may be normally maintained in the position shown, a spring cage 44 is provided having its left end maintained in engagement with the right surface o the piston by means 0f a spring 45 interposed between the left end of the cage and the casing, further movement of the cage to the left being prevented by means of a flange i6 formed thereon and adapted to engage a flange Lil formed on a washer 48 rigidly positioned shown at the right end of the casing. It will. also be noted that the flange portion fili is so dimensioned to permit movement of the piston to the right with consequent compression ci the spi .ig c5. In like manner, the piston is positioned against movement in the opposite direction by means of a spring cage 49, a spring 5D, and a hanged washer 5 i. Leakage of iluid pressure from the chambers 42 and 43 through the bores 38 and 39 is prevented by means of suitable seals 52 and 53 respectively. Thus it will be apparent that on application of uid pressure to the chamber 43 through the port 36, the piston 40 will be moved to the right against the force exerted by the spring 45, and after a pre determined degree of movem-ent in this direction, the piston will move to the right of the annular portion 4| suiiiciently to permit the iiow of fluid pressure from the chamber 43 to the chamber 42 between the piston and the wall of the passage. In the event the pressure in the chamber 42 is greater than th-e chamber 43, the reverse action will take place, and when the pressures in the two chambers are substantially equalized, the springs 45 and 50 and their associated cages will act to :again return the piston to the position shown and to maintain it in this position until a predetermined pressure differential is again established in the two chambers.

Switches are provi-ded for controlling the energization of the magnet valve, and these switches are preferably of the snap action type for the purpose of minimizing arcing and burning of the contacts, and may be constructed in a manner similar to that shown in a patent to Riche, No. 2,181,068. As indicated more particularly in Fig. 1, a controller bracket 54 is suitably attached to the vehicle and also to the casing 33, by means not shown, and switches 55 and 56 are suitably attached to the bracket 54, The switch 55 is shown in partial section, and is preferably of the type disclosed in the above referred to Riche patent. A contact carrying spring member 56a is mounted in the switch 55, as shown in more detail in Fig. 3, the upper en-d of the spring being normally in engagement with a stop 51 which is insulated from the remainder of the switch. A contact 58 is provided on the upper end of the spring, and is adapted on movement to the left to engage a contact plate 59 suitably connected with a terminal 6B, the lower end of the spring being connected with a terminal 6l. As shown more fully in Fig. 3, a member 62, of dielectric material, is mounted to engage a portion 63 of the contact spring, the member being provided with an operating plunger 64. Since a resilient or collapsible connection is desired for operating the switch, as will be more fully explained hereinafter, such a connection is provided by means of a hollow plunger 65, slidably mounted in the switch and operatively connected with the plunger 64 by means of a relatively light spring 56 interposed between the plungers 65 and 64, movement of the plunger 65 to the right with relation to the switch being limited by means of a shoulder 61 formed thereon. Thus on movement of the plunger 65 to the left, as shown in Fig. 3, the plunger 64 and the member 62 will move the portion 63 of the contact spring to the left, and as will be well understood by those skilled in the art, the upper end of the contact spring will immediately move with a snap action from the position shown to a position such that the contact 58 is in engagement with the contact plate 59, thus establishing an electrical connection between the terminals 60 and 6l of the switch. The switch 56 of similar construction, is mounted at the right side of the bracket 54, and is provided with terminals 68 and 69 and an operating plunger 'I0 having a construction similar to that provided on the switch 55. With the parts in the position shown, the contacts of both switches are open, and on movement of the' plungers 65 and 10 to the left and right respectively, the switch 55 or the switch 56 will be operated to establish a connection between terminals 60 and 6l or terminals 68 and 69. The switches are mounted in such a manner that with the contacts in open position, the inner ends of the plungers 65 and 'I0 are substantially in engagement respectively with the left and right ends of the piston rod 37, Thus on initial movement ofthe piston to the right, the switch 56 is operated to connect terminals 68 and 69, while on movement of the piston to the left from neutral position, the switch 55 is operated to connect terminals 60 an-d 6|. The length of the piston in relation to the formation of the annular portion 4i of the passage 34 is so dimensioned as to permit operation of the switches before suiiicient movement occurs to permit communication between chambers 42 and 43 by the piston. In the event a suiiicient pressure differential is established across the piston, the springs associated with the plungers 65 and 10 are such as to permit this further movement of the piston after operation of the switches in order to establish such communication.

The vehicle is provided with a suitable battery or source of electricity ll, having one terminal connected with the upper end of a switch bar 12 by means of a wire 13, and the other terminal connected with the terminals 29 and 30 of the magnet valve 2| by means of wires 14, 15 and 16. The terminal 28 of the magnet valve portion 22 is connected with the terminal 68 of the switch 56 by means of wires Tl and T8, the terminal 69 being connected with a switch terminal 'I9 by means of wires and 8l. The switch terminal 19 is so positioned that on movement of the switch bar l2 in a counterclockwise direction, the latter engages the terminal 19 and completes the circuit through the magnet valve portion 22 by means of the connections just described. 'Ihe terminal 3l of the magnet valve portion 23 is connected with the terminal 6l of the switch 55 by means of wires 82 and 83, the terminal 69 of the switch being connected with the terminal 'i9 by means of wires 80 and 8|. In order that the electromagnet portion of the system may be ineffective when the vehicle is inoperative, an additional switch contact 84 is provided having a wire 85 connected in a conventional manner with the ignition coil, the switch bar thus being operative to energize the ignition circuit and the circuit for the magnet valves at the same time.

As heretofore stated, the brake valve I5 is designed to supply fluid pressure to the conduit i8 at pressure substantially proportional to the degree of movement of the control pedal 29 from the position shown. Assuming that the pedal is operated to supply a given pressure to the conduit i8, it will be understood that this pressure will be supplied to the chamber 43 of the controller, and that due to the positioning of the piston 4D, the chamber 42 will still remain at substantially atmospheric pressure during initial operation of the brake valve. This pressure differential will move the piston to the right, whereupon the plunger 'lil will be depressed, and the switch 56 will be operated to connect terminals 68 and 69. When this occurs. the portion 22 of the magnet valve will be energized and communication will be established between conduits 24 and 25, thus supplying fluid pressure lfrom the reservoir i4 directly to the portion. of the conduit I8 shown at the right side of the controller 32. Thus pressure will likewise be conveyed to relay valve Il! through the conduit Il, and the relay valve will operate to establish 7 communication between conduits i2 and i3, thus supplying fluid pressure directly from the reservoir iii to the actuator As the pressure increases in the right hand portion oi the conduit lil, the pressure will likewise increase in the chambei' of the controller, and when the pressure diierential between the chambers becomes insufficient to maintain the piston and piston rod in their right hand operating positions, the spring will more the piston and rod to the left sufficiently' to permit the contacts oi the switch to ln-ove to open position. Thus he cle-energization oi the portion 22 ci the magnet valve prevents the further supply oi fluid pressure rorn the reservoir irl to the right hand portion o the conduit it. rlhis action will occur when the pressure in the chamber d2 is substantially the saine as that in the chamber 3, and consequently the ultimate pressure reached in the conduit ii well as in the actuator il will ce substantially the same as that supplied to the conduit it? and to the chamber :it by the operation ci the brake valve Assuming that a predetermined pressure has been established in the conduit and in the actuator in the rn .ler above described, it will be apparent that on release movement o the brake pedal 2t, the ccndu ifi will connected with the exhaust conduit lil in or er to exhaust huid pressure to iospliere, and the ressure in the left portion of the coi i' iB in the chamber i l be r"- ured to a new value which is determioed by the new setting of 'the brake pedal 2C?. when this ac- 'ie pressure in the chamber will be ess ci" that inthe chamber 3, and the piston ici/ed to 'the left to close the contacts of da and energize the portion or" the vaiv'e to establish communication beright h :l portion of the conduit i8 :iaust c l duit 2l through conduits 25 magnet valve portion will const fluid prmsure in manner unthe c ambers u; and are all;T equalized, at which time the ttul will n be nice/ed to neutral position by t' n or" the si 'ing and contacts of vit-ch will open or er to cle-energize the When this action ocrs, t. the conduit lil, chambers and fl the con .t li, the conduit and the actuator 3 will again be substantially proportional to the degree oi movement ci the control pedal from it normal release position, it being understood that the above release of iluid pressure :from the conduit lil by the operation ci the magnet valve, tl e fluid pressure operated device or relay valve l is likewise eilective to proportionally release iluid pressure from the actuator t. a controller has been provided which is remonsive to diierences in pressure in the two por ions oi the conduit t5 for controlling the energization of the application and exhaust portions of the magnet valve, in order to maintain a pressure in the right portion of the conduit I3 and in conduit i l leading to the relay valve which is substantially proportional at all tirnes to that delivered to the left portion of the conduit i8 by the operation ci' the brake valve i6, and due to the with whici the magnet valve is energized and cle-energized, and due to the small volume represented by the left portion of the conduit i8 and the controller chamber d3, the speed of application and release of the vehicle brakes is naturally much faster than is the case in a system ci the more conventional type.

Due to the possibility of fail-ure of the electrical portion of the system for seine reason, such as the breaking ci one ci the wires, it is also desirable that the brake valve be effective to supply fluid pressure directly to the upper end of the relay valve through the conduit IS and the conduit II in the event oi such failure, and as heretofore explained, the switch p-lungers and are of a collapsible nature, and are so constituted as to ypermit movement of the piston in either direction alter closing of the switch contacts sufficiently to allow the outer surface of the piston to move away from the annular portion il ci 'the chambers 43 The pressure diierential at which this action occurs is determined by the tension of the neutralizing springs and 5i! and the collapsible springs in the plungers i555 and lil, and the tension of these springs is preferably so chosen as to permit movement of the piston suiiicicntly to establish communication between chambers 43 and 42 as soon as a relatively small pressure diierential, on the of one or two pounds, for cXample, is

hed across the piston. lluring normal opi of the system, with electioniagnet valve effec ve, the build-up of pressure in the chamber f-f. is sc rapid as to prevent sufficient movement of the piston to the right to establish communication between 'the two chambers of the contr ller when the brake valve pedal is operated to effect an application of the brakes, and in like inant. ie exhaust oi fluid pressure from the right portion of the conduit l and from the chamber ./li i so rapid on operation of the magnet valve to prevent sufficient moi/erneut of the piston to the left to allow the exhaust of fluid pressure yfrom the right portion of the conduit li and :from the conduit i l through the exhaust port of the brake valve. In the event oi failure of the electrical portion of the system, however, the operator only to operate the brake pedal in the L ai man,e or, whereupon the pressure supplied to the cha' l :l5 ci the controller immediately ino-i the sten to the right s ntly to establish relatively unrestricted com -unicatlon between the chambers l2 and Thus the brakes will be appli by the operator in the usual manthe only difference being that the operation is somewhat slower t. i is the case when the electrical ortion of the is operative, and that the pressure supplied to the right portion of the conduit it anc to the conduit l! is slightly less than that supplied to the lei-t portion of the conduit iS due to the diiierential pressure set up by the pist-on 4B and the springs which oppose its movement to the right. During release operation ci the brake valve the piston likewise is moved to the left by virtue ci the greater pressure in the chamber 42, and communication is established between chambers fifi and in order to permit the exhaust of iiuid pressu 'e from the right `portion of the conduit iS and from the conduit l i through the brake valve.

Systems of the above type are particularly advantageous in connection with trailer-tractor trains in view of the relatively long lengths of the fluid pressure supply and control conduits, and the system may be readily applied to a trailer in the manner sho-wn more particularly in Fig. 1--a. The right end of the conduit E8 in Fig. l is provided with a shut-oir valve Sii and a detachable coupling the latter being connected to a control ccnduit S carried by the trailer. A supply conduit or feed line S9 is also mounted on the trailer and connected with the tractor reservoir lil through a detachable coupling a shut-01T valve Si, and a conduit S2. The valves 86and g.. 9| are' normally closed when the tractor only is in operation, and when the trailer is attached to the tractor, the valves are opened in order to permit the ilow of fluid pressure to the con-duits 98 and B9 respectively. The trailer is likewise equipped with a fluid pressure brake system of conventional type comprising a trailer reservoir 92, a iluid pressure operated brake actuator 93, and a relay emergency valve 99 which may be constructed in accordance with the principles set forth in the patent to Stephen Johnson, Jr., No. 2,018,212, dated October 22, 1935. This valve is provided with a relay portion 95 having a control conduit 96 connected with the control conduit 93 and a supply conduit 9'1 connected with the trailer reservoir 92. An emergency valve portion 99 is provided with an outlet conduit 99 connected with the actuator 99, and a feed conduit |99 connected with the feed or supply line 89 leading from the tractor to the trailer. The relay valve portion is also provided with an exhaust port, not shown, the construction being such that fluid pressure is normally supplied to the trailer reservoir 92 from the conduit S9 through the conduit |00, the emergency valve portion 99, the relay valve portion 95, and the conduit 97|. The construction of the emergency valve portion is such that in the event of sudden drop of pressure in conduits |99 and 89, the emergency valve portion is effective to establish communication between conduits 91 and 99 to supply i'luid pressure from the trailer reservoir to the actuator at reservoir pressure, and is also effective to prevent the reverse iiow of fluid pressure from the reservoirthrough the relay emergency valve into the broken conduit 89. The relay valve portion is so constituted as to normally connect conduit 99 with atmosphere, and to prevent communication between conduits 91 and 99, the application of a predetermined pressure to the relay valve through the conduit 99 serving to operate the latter to supply fluid from the reservoir 92 to the conduit 99 and the actuator 93 at a pressure substantially equal to that obtaining in a conduit 95. Since the control conduit 98 is connected to the control conduit on the tractor, and the conduit 89 is connected to the tractor conduit leading to the supply reservoir Ii on the tractor, the trailer reservoir 92 is at all times charged with fluid pressure from the tractor, and an increase in pressure in the control conduit 88 results in corresponding operation of the relay valve por tion or fluid pressure operated device 95 of the emergency valve to supply a substantially corresponding pressure to the actuator 93.

Here again the speed of operation in supplying fluid pressure from the reservoir to the trailer actuator is somewhat impaired by the length of the control conduit between the tractor and trailer, and to this end a duplex electromagnet valve IOI, preferably identical with the valve 2| on the tractor, is suitably mounted on the trailer adjacent the relay emergency valve 94. This valve is provided with a supply conduit |02, and outlet conduit |03, an exhaust conduit |04, and a conduit |05 which serves to connect the outlet conduit |93 with the exhaust portion of the electromagnet valve. It will be understood, therefore, that with the magnet valve deenergized, the latter serves to prevent communication between conduits |92 and |03, as Well as between conduits and |04. When the left hand portion of the valve is energized, conduits |02 and |03 are connected, and when the right hand portion of the valve is energized, conduits and |04 are connected. The left hand portion of the valve is provided with magnet coil terminals |06 and |91, the right hand portion being provided with terminals |08 and |09. The terminals |07 and |98 are interconnected by means of a Wire H0, the latter wire being connected to the wire i4 on the tractor by means of a wire iii. In like manner, the terminal |09 is connected with the wire 83 on the tractor by means of a wire i2, and the terminal |96 is connected with the wire 'E8 on the tractor by means or a wire I i3. Thus the application and release portions of the valve IOI are connected in parallel with the corresponding portions of the tractor electromagnet valve 2|, and on operation of the switch to energize the portion 22 of the magnet valve l. I, the left hand portion of the trailer magnet valve I9I is likewise energized to connect conduits E92 and |03 in order to supply uid pressure to the latter conduit and to the conduit 96 to operate the relay valve to supply fluid pressure from the trailer reservoir 92 to the trailer brake actuator 99. On operation of the switch 55 to energize portion 23 of the tractor magnet valve, the right hand portion of the magnet valve I0| is likewise energized to connect conduits |05 and 94 in order to exhaust fluid pressure from conduit I 93 and conduit 96 leading to the relay valve, the result being that the relay valve is eiective to correspondingly release pressure from the actuator 93.

Since the trailer magnet valve I0| preferably has a relatively large uid pressure flow capacity, and operates substantially instantaneously in response to operation of the application switch to on the tractor, it will be apparent that such operation of the magnet valve during application of the brakes may result in a rapid drop in piressure in the supply conduit |92 unless means are provided for rapidly supplying iluid pressure from the source to that conduit. Thus in the event conduit |92 were directly connected with the trailer supply conduit 89, it Will be apparent that operation of the magnet valve during a brake application might eiect a suicient reduction in pressure in the conduit 89 to initiate operation of the emergency Iportion 99 of the relay emergency valve to eect an emergency application oi the trailer brake. This action is undesirable, and in order to minimize the drop in pressure in the line during operation of the magnet valve, a relatively small auxiliary Lreservoir IM is connected at one end to conduit |92, and is connected at the other end with the conduit 89 by means of a :conduit I i5 and a one-way check valve I I9 as shown, the check valve being so arranged as to permit the flow of fluid pressure from the conduit 99 to the conduit H5, and to prevent flow in the opposite direction. rEhe capacity of the reservoir I Ill is so chosen as to prevent a drop in pressure in the conduits I I5 and 89 suiiicient to operate the emergency valve when the magnet valve is operated to `supply fluid pressure to the brake system. As an additional safe guard, a restricted portion I|`| is provided in the :conduit I I5 which serves to limit the rate of flow of uid pressure to the auxiliary reservoir II4. The size of the restriction IiI can be so chosen as to eliminate an unwanted emergency application of the brakes on operation of the magnet valve, but in the event such a restriction is incorporated in the conduit II5, the reservoir I I4 becomes necessary in order to provide .sunicient iiuid pressure supply to the magnet valve for each individual brake application. In the event of a rupture in the conduit 89 at the left ofitsjunction with the conduit I B0, the emergency portion4 9i!AY normally operates to effect an emergency application. of. the trailer brakes. With thecapacity ofthe auxiliary reservoir H4 connected to the conduit 89, however, it will be apparent thatunless the check valve IIS is provided, nuidpressure will'flow4 from the reservoir I I/lfthrough the conduit II 5to the conduit 89, and the amount of this -ow due to the capacity of the reservoir may be suilicient to prevent operation of the emergency portion 98 to effect a desired emergency application ofthe trailer brake, as the flowof this-additional fluid into the conduit B willfcause the pressure in that conduit to drop ata much slower |rate than would normally occur in the event of lbreakage of the conduit. Thus the reservoir IM, the restriction-I Il and the oneway'checl; valve H6 are all effective toprevent interference with the normal functions of the emergency portieri of the relayemergency valve due to the incorporation of the magnet valve in the'systern', and; at the same time, the arrangement shown insures yan-adecniate supplyoi' iiuid pressure to the inlet conduit or supply conduit to2 of the magnet valve to insure satisfactoryoperation ofthe'magnet valve in controlling the operation ofthe brakes.

In` View ofthe foregoing description, it will be readily apparent to those slilledn the art that a relatively simple and efficient electromagnet control has been provided for a tractor, or atractor-trailer brake system, so constituted as to lbe readily applied to existing syste-ms without materially interfering withthe normal functions of the originalsystom. In the event oi failure in the electrical-portion of the system, the controller is effective to by-pass iiuidpressure from` the left hand portion of the conduit I8 into the right handportion of the conduitiandint-o the trailer control 'conduit 8B, this Llid gplessure being; transmitted to vthe tractor andtrailer relay valve portions I and 95 respectively, in order to operate the latter to supply' fluidA pressure to the corre spending. 'brake actuatorsfrom the reservoirs if; and 9121.' `When the electrical Vportion ofthe system is operative, the initial application of fluid pressure to the chamber in the left end oi the controller by operation of the brake valve, effects operation of the switch S rto instantly energize the application portions of the magnet valves El and Il vin order to supplyV iiuid pressure to the right hand portion of conduit I8 and'to cond-uit Sil-untilsuch time as pressure thereinsubstantial.- ly' equals that inthe leit-handportionof the conduit I8, at which time the application portionsA ofethe magnet valves arado-energized, and the system is in lapped position, the same type ci operation taking place on'release operationoithe brake valve. In addition to theforegoing, [means have beenr provided on the trailer for supplying fluid pressure to the trailer magnet valve, so constituted `as to Ipermit operation of this valve without interference-with the normal `functioning of the emergency DOrtion of the trailer relay emergency valve. The controller is also adapted to readily operate switches ofthe so-called snap action type, thus eliminating many difficulties due to arcing and burning` of the switch contacts which have caused ,diiiiculty in some of the previous systemsof this `general type. Also, while the magnet valves in the above systems have'been shownas. adapted to supplyl fluid pressure to iluidpressure operated devices such as the relay valvesillustrated; and `it will ybe Aunderstood that inthe `event the relay .valves -are -dispensed with,

the magnet' valve outlet lines 25 and |03 can readily be connected to supply iiuid pressure directly to the tractor and trailer brake actuators 8 and 93 respectively.

Although the invention has :been illustrated and' described herein with considerable particularity, it is to be understood that the salme is not limited to the form shown, but may receive a variety of mechanical expressions, as will now read" ily appear to those skilled in the art.. Reference will, therefore, be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a fluid pressure brake control system of the type having a source of fluid pressure, a fluid pressure actuated braking device, means including power operated valve means for controlling the flow of fluid pressure from the source to the device and for controlling the release of fluid pressure from the device, a connection for supplying fluid pressure to said device, and a control valve for supplying uid pressure to said connection, and for releasing fluid pressure from said connection, the improvement which comprises a controller interposed between said control Valve and connection having a pressure responsive member responsive jointly to the pressure supplied by the control valve and the pressure in the connection normally positioned to prevent communication between the control valve and said connection and movable in either direction in response to variations in pressure in the control valve and in said connection to establish communication between the control valve and said connection, means for selectively energizing said power operated valve means to supply uid pressure from the source to the device and to release fluid pressure from the device, and an operative connection between said member and energizing means operable on initial movement of the member in one of said directions to render the energizing means effective to energize the power operated valve means to supply fluid pressure to said device and operable on initial movement of said member in the other of said'directions to render the energizing means effective to energize the power operated valve means to release fluid pressure from the device.

2. In a fluid pressure brake control system of the type having a sourcevof fluid pressure, a iiuid pressure operated braking device, means including an electromagnet valve for supplying iluid pressure from the source to the device, a connection for supplying fluid pressure to said device, and a control valve for supplying fluid pressure to said connection, the improvement which comprises a controller interposed between said control valve and connection and having a pair .of chambers, one chamber being connected with the control valve and the otherchamber being connected with said connection, a pressure responsive member .movably mounted in said controller subjected to the pressures in both chambers, said member being normally positioned to prevent communication. between the chambers and being movable in response to an increase in pressure in said one chamber to establish' communication between said chambers, means including a switch forenergizing said electromagnet valve to supply uid pressure to the device, and an operative connection between said member and switch operableon initial movement of said member to close said switch and energize said electromagnet valve.

3.v In a fluid pressure brake control systemv of the=type having a sourceof iiuid pressure,` a iiuld pressure operated braking device, means including an electromagnet valve for supplying fluid pressure from the source to the device, a connection for supplying fluid pressure to said device, and a control valve for supplying fluid pressure to said connection, the improvement which comprises a controller interposed between said control valve and connection and having a pair of chambers, one chamber being connected with the control valve and the other chamber being connected with said connection, a pressure responsive member movably mounted in said controller subjected to the pressures in both chambers, said member being effective in one position to prevent communication between said chambers and movable to another position in response to an increase in pressure in said one chamber to establish communication between said chambers, means including a switch for energizing said electromagnet valve to supply fluid pressure to the device, an operative connection between said member and switch operable to close the latter to energize the electromagnet valve on movement of the member from said one position toward said another position, and means for maintaining the member in said one position except when the pressure in said one chamber exceeds the pressure in the other of said chambers by a predetermined value.

4. In a fluid pressure brake control system of the type having a source of fluid pressure, a fluid pressure operated braking device, means including an electromagnet valve for supplying fluid pressure from the source to the device and` a sec-- ond electromagnet valve for releasing fluid pressurev from the device, a connection for supplying iiuid pressure to the device, and a control valve for supplying fluid pressure to said connection and for releasing fluid pressure from said connection, the improvement which comprises a controller having a pair of chambers, one chamber being connected to the control valve and the other being connected to said connection, a pressure responsive member movably mounted in said controller subjected jointly to the pressures in both chambers, said member being eiiective in one position to prevent lcommunication between said chambers and operable on movement in either direction from said position to establish communication between said chambers, means for energizing said valves including a switch for the supply electromagnet valve and a switch for the release electromagnet valve and an operative connection between said member and switches operable on movement of the member in one direction from said one position to close one of the switches to energize the supply electromagnet valve and operable on movement of the member in the other direction from said one position to close the other of said switches to energize the release electromagnet valve.

5. In a fluid pressure brake control system of the type having a source of fluid pressure, a fluid pressure operated braking device, means including an electromagnet valve for supplying fluid pressure from the source to the device and a second electromagnet valve for releasing fluid pressure from the device, a connection for supplying fluid pressure to the device, and a control valve for supplying fluid pressure to said connection and for releasing iiuid pressure from said connection, the improvement which comprises a controller having a pair of chambers, one chamber being connected to the control valve and the other chamber being connected to said connection, a pressure responsive member movably mounted in said controller subjected jointly to the pressures in both chambers, said member being eiective in one position to prevent communication between said chambers and operable on movement in either direction from said one position to establish communication between said chambers, resilient means for normally maintaining the member in said one position, means for energizing said valves including a switch for the supply electromagnet valve and a switch for the release electromagnet valve, and an operative connection between the member and switches operable on movement of the member in one of said directions from said one position to close one of the switches to energize the supply electromagnet valve and operable on movement of the member in the other of said fdirections from said one position to close the other of said switches to energize the release electromagnet valve.

6. In a fluid pressure brake control system of the type having a source of fluid pressure, a fluid pressure operated braking device, means including an electromagnet valve for supplying fluid pressure from the source to the device and a second electromagnet valve for releasing fluid pressure from the devicey a connection for supplying fluid pressure to the device, and a control valve for supplying fluid pressure to said connection and for releasing uid pressure from said connection, the improvement which comprises a casing having a pair of chambers, one chamber being connected to the control valve and the other chamber being connected with said connection, means for energizing said valve including a switch for the supply electromagnet valve and a switch for the release electromagnet valve, and means operable when the pressure in the first named chamber exceeds the pressure in the second named chamber by a predetermined value for operating one of the switches to energize the supply electromagnet valve and operable when the pressure in the second named chamber exceeds the pressure in the first named chamber by a predetermined value for operating the other switch to energize the release electromagnet valve including a movable pressure responsive member subjected to the pressures in both chambers and an operative connection between said member and switches, said member being operable to prevent communication between the chambers when the pressures therein are substantially equal and movable to establish communication between said chambers when the difference in the pressures in said chambers exceeds said predetermined value,

7. In a fluid pressure brake control system of of the type having a source of fluid pressure, a fluid pressure operated braking device, means including an electromagnet valve for supplying fluid pressure from the source to the device, a connection for supplying fluid pressure to said device, and a control valve for supplying ui'd pressure to said connection, the improvement which comprises a controller interposed between said control valve and connection having a pair of chambers, one chamber being connected with the control valve and the other chamber being connected with said connection, a pressure responsive member movably mounted in said controller subjected to the pressures in both chambers, said member being normally positioned to prevent communication between the chambers and being movable in response to an increase in pressure in said one chamber to establish communication between said chambers, means including a switch for energizing said electro-magnet valve to supply fluid pres- 15 sure to the device, and means for operating said switch to energize said electromagnet valve rduring initial movement of said member and for permitting further movement of said member to establish 'communication between said chambers including a' resilient operating connection between said member and switch.

8. In a iiuid'pressurebrake controlsystem of the type having a source of fluid pressure, a iiuid'pressure operated braking device, means including an electromagnet valve for supplying fluidv pressure from the source to' the device and a second electromagnet valve for releasing iiuid pressure from the device, a connection for supplying fluid pressure to the device,

a control valve for supplying fluid pressure to the connection andfor releasing fluid pressure from the connection, the improvement which comprises a pairv of snap action switches for connecting a source of electrical energy respectively with the supply electromagnet valve and with'the release electromagnet valve, and means for selectively operating said switches and controlling the flow of huid pressure between said control valve and said connection including a controller having a pair of chambers, one chamber being connected to the control valve and the other chamber being connecte'dto said connection, a pressure responsive member mounted in said `controller subjected to the pressures in said chambers, said member being eliec'tive in one position to prevent communication between said chambers and being movable in either direction from said position in response to diierences of pressure in said chambers to establish communication therebetween, and a yresilient-operating connection between said member and each of said switches.

9. In a fluid pressure brake control system having a source of iiuid pressure, a fluid pressure brake actuator, and a iluid pressure operated relay valve for Icontrolling the supply of iiuid pressure from the source to the actuator and for controlling the release 'of uid pressure from the actuator, means for controlling the operation of the relay valve including an electromagnet valve for supplying fluid pressure thereto to operate the relay valve to supply fluid pressure from the source to the actuator and a second electromagnet valve for releasing iiuid pressure from the relay valve whereby the latter is operable to release iiuid pressure from the actuator, a self-lapping control valve having a connection with the source and a connection with the relay valve, the improvement which comprises means for controlling the energization of said magnet valves and the flow of :fluid pressure in said last named connection including a controller interposed in sai-d connection having a passage connected at one p0rtion with the operators control valve and at another portion with the relay valve, a'pressure responsive member movably mounted in said passage operable to vnormally prevent the passage of fluid pressure therethroughl and operable on movement through a predetermined distance in response to pressure differentials acting thereon to permit the ow' of uid pressure through said passage, and means for energizing said magnet valves including switch means having an operating connection with said pressure responsive member and actuated by initial movementof thc member in one direction to energize the iirst named magnet valve and by initial movement in the other direction to energize the second magnet valve.

10. In a brake system of the type having` a source of :Huid pressure, a brake chamber, a relay valve for connecting said source and chamber, electromagnet valves for controlling said relay valve, and a brake valve having a iirst` connection with said source and a. second connection with the relay valve and electro-magnet valvesy the improvement which comprises a Acontroller having a casing in series with the second connection, a pair of snap-acting switches mounted outside of said casing for controlling said electro-magnet valves, and a pressure responsive member within the casing mounted to move in opposite directions lin response to relatively low pressure differentials to operate said switches while substantially preventing fluid flow through said casing, and movable in response to relatively higher pressure differentials to establish fluid flow through said casing.

ELLERY R. FITCH.

yRn'FrnnzNo13s CITED The following references are of record in the I'ile of this patent:

lUNITED STATES PATENTS Number Name Date 2,018,212 Johnson oet. 22, 1935 2,052,204 Logan Aug, 25, 1936 2,091,046 Hewitt Aug. 24, 1937 2,136,577 Campbell Nov. 15, 1938 2,147,296 Farmer Feb. 14, 1939 2,234,897 Eaton Mar. 11, 1941 2,360,659 Eaton Oct. 17, 1944 

